U.S. Pat. No. 4,906,895, Pabst et al., assigned to the assignee of the present application, discloses a high-pressure discharge lamp which has means to quiet the arc. According to this disclosure, the cathode, at least in the region of a tapered tip, is covered with a carbide layer. The thickness of the carbide layer continuously decreases towards the tip or leaves the tip region, approximately one-third of the length of the tapered tip, entirely free of carbide.
It has been found in operation and use that the stability of the arc can be improved, this is particularly important when lamps of this type are used in photometric applications. The manufacture of arc lamps with such tips is comparatively time-consuming and hence expensive.